The invention relates to a liquid-ring vacuum pump having a shaft which is mounted eccentrically in a pump housing. An impeller and a rotor of a drive motor are connected to the shaft. A control disk is arranged parallel to the impeller.
Pumps of this type can be used for evacuating containers or other closed spaces. An inlet opening of the pump is connected to the space to be evacuated, the gas which is contained in the space is sucked into the inlet opening, is compressed in the pump and is output again through an outlet opening.
In liquid-ring vacuum pumps, a liquid ring is kept in motion by way of the impeller, with the result that the chambers between the vanes of the impeller are closed by the liquid ring. Since the impeller is mounted eccentrically in the pump housing, the liquid ring penetrates to different extents into the chamber depending on the angular position of the impeller and, as a result, acts as a piston which changes the volume of the chamber. The entire force which is required for this purpose is transmitted by the shaft and the impeller.
Liquid-ring vacuum pumps of monobloc design classically consist of a standard electric motor and the pump which is flange-connected thereto fixedly. The pump and motor are separated hydraulically with the aid of a slide ring seal. The pump does not have any dedicated bearings, with the result that the bearings of the electric motor are used to absorb the process forces. Said bearings are normally reinforced. The process forces act in the radial and the axial direction on the cantilevered impeller and subject the shaft to a compressive load and, above all, to a bending load. This deflection has to be taken into consideration during the design of the pump by sufficient tolerances being provided. In particular, a distance has to be maintained between the impeller and the control disk because deflection of the shaft otherwise leads to the impeller otherwise butting against the control disk. However, tolerances between the impeller and the control disk are associated with leakage losses which reduce the degree of efficiency of the pump.